Apparatus and method for comparing output signals indicative of engine rotational speed and/or generator rotational speed

ABSTRACT

An apparatus and method are provided to deliver a pair of output signals indicative of engine rotational speed and/or generator rotational speed. The signals are compared to each in order to determine if a generator is operating properly. At least one output signal is delivered to, or developed internally and used by, a voltage regulator of the generator. One output signal is generated based on a ripple on a positive voltage input to the voltage regulator from a generator. The other signal is indicative of the voltage at the rectifier bridge.

TECHNICAL FIELD

The present application relates to an apparatus and method for comparingoutput signals indicative of engine rotational speed and/or generatorrotational speed. The present invention also relates to a voltageregulator adapted to determine engine rotational speed and/or generatorrotational speed based on a ripple on a positive voltage input to thevoltage regulator from a generator, and a charging system containingsuch a voltage regulator.

BACKGROUND

Voltage regulating systems for controlling the field current of adiode-rectified alternating current generator, that supplies theelectrical loads on a motor vehicle, are known to those skilled in theart. One type of voltage regulator senses the voltage applied to thebattery, and if this voltage is higher than a desired regulated value, atransistor that controls field current is switched off. When generatorvoltage drops below the regulated value, the field controllingtransistor is switched on. The transistor is repetitively switched onand off in response to sensed voltage changes to thereby cause theoutput voltage of the generator to be maintained at a predetermined,desired regulated value.

In another type of voltage regulator the field current is pulse-widthmodulated at a constant frequency to maintain the output voltage of thegenerator at a desired regulated value. The pulse width, in this type ofsystem, is a function of the difference between actual generator outputvoltage and a desired voltage. Examples of this type of regulator aredisclosed in U.S. Pat. No. 2,976,473 to Shaw et al. and U.S. Pat. No.4,275,344 to Mori et al. British Pat. No. 1,392,096 also disclosespulse-width control of field current, and in that patent, the voltagereference takes the form of a cyclic staircase waveform.

Another voltage regulator that employs pulse width modulation ofgenerator field current is disclosed in U.S. Pat. No. 4,636,706 toBowman et al., the contents of which are incorporated herein byreference. According to Bowman et al., the regulator disclosed in thatpatent utilizes a digital apparatus that includes an up-down counterwhich responds to the relative magnitudes of the actual output voltageof the generator and the desired regulated output voltage of thegenerator. When the actual output voltage of the generator is below thedesired regulated value, the counter is incremented or counted up, andwhen the actual output voltage is above the desired regulated value, thecounter is decremented or counted down. The instantaneous count in thecounter is used to determine the on time of a semiconductor switch thatis connected in series with the field winding of the generator. Theinstantaneous count thus determines the pulse-width of the voltage thatis applied to the field. Whenever actual output voltage exceeds thedesired regulated value, the field controlling semiconductor switch isbiased off. Thus, during the time that the actual output voltage isabove the desired regulated value, the field is not energized and thecounter is decremented. When actual output voltage then drops below thedesired regulated value, the field is energized at the pulse-widthrepresented by the magnitude of the count in the counter, and thecounter is incremented.

A particularly advantageous feature of the Bowman et al. voltageregulator is its ability to adjust the counting rate of the counterbased on engine speed. By suitably adjusting the counting rate, thevoltage regulator is able to minimize the increased torque load that isapplied to the engine by the generator when a large electrical load isapplied to the generator at the time that the engine and generator areoperating at a low speed such as engine idle speed. Thus, during engineidle, field current is gradually increased so as not to impose a suddentorque load on the engine when a large electrical load is applied to thegenerator. Since this type of voltage regulator is responsive to enginerotational speed and/or generator rotational speed, it requires an inputsignal indicative of that speed.

According to the Bowman et al. patent, this input signal is provided bytapping one of the stator winding phases. This phase of the statorwinding is tapped by electrically connecting the appropriate inputterminal of the voltage regulator to an AC node of the bridge rectifierthat is connected to that phase. FIG. 1 shows a line 7 from node 32 tothe voltage regulator as an example of such an electrical connection.

SUMMARY

An apparatus and/or method for providing an output signal indicative ofengine rotational speed and/or generator rotational speed, and/or byalso providing a voltage regulator adapted to determine enginerotational speed and/or generator rotational speed based on a ripple ona positive voltage input to the voltage regulator from a generator,and/or by providing a charging system containing such a voltageregulator. The apparatus compares the compares the signal based uponripple on a positive voltage input to an input signal that is providedby tapping one of the stator winding phases. If the there is adifference in the two signals an indicator light will be activated and,if necessary, the system is shut down.

An apparatus and method are provided to deliver a pair of output signalsindicative of engine rotational speed and/or generator rotational speed.The signals are compared to each in order to determine if a generator isoperating properly. At least one output signal is delivered to, ordeveloped internally and used by, a voltage regulator of the generator.One output signal is generated based on a ripple on a positive voltageinput to the voltage regulator from a generator. The other signal isindicative of the voltage at the rectifier bridge.

Still other objects, advantages, and features of the present inventionwill become more readily apparent when reference is made to theaccompanying drawings and the associated description contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a charging system that includes anapparatus for generating a speed-indicative signals according to apreferred embodiment of the present invention;

FIG. 2 is a schematic illustration of a preferred implementation of aportion of the speed signal circuitry shown in FIG. 1;

FIG. 3 is a timing diagram that shows different signals that appear in aportion of the speed signal circuitry of FIG. 1, as well as a phasesignal developed at an AC input terminal of a bridge rectifier; and

FIG. 4 is schematic illustration of a comparator.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a motor vehicle electrical charging system 2according to a preferred embodiment of the present invention. Thecharging system 2 includes a voltage regulation unit 4 and a speedsignal apparatus 6 which, as will be described hereinafter, is adaptedto provide the voltage regulation unit 4 with a signal indicative of therotational speed of a generator 10 and/or engine 16 associated with thecharging system 2.

An exemplary speed signal apparatus 6 is disclosed in commonly owned andassigned U.S. Pat. No. 6,215,285 the contents of which are incorporatedherein by reference thereto.

Preferably, the generator 10 of the charging system 2 is provided in theform of an alternating current generator 10. This alternating currentgenerator 10 has a three phase Delta-connected stator winding 12 and arotatable field winding 14. The generator 10 is capable of generatingmulti-phase AC output currents via the stator winding 12 when the statorwinding 12 is excited by the rotatable field winding 14.

The generator 10 may be of the type disclosed in the U.S. Pat. No.3,538,362 to Cheetham et al. with the exception that the generator inFIG. 1 has a Delta-connected stator winding rather than the Y-connectedstator winding shown the Cheetham et al. patent. It will be understood,however, that the voltage regulation unit 4 and speed signal apparatus 6of this invention can be used with generators that have either Delta orY-connected stator windings.

The field winding 14 is part of a rotor assembly which is rotatablydriven by the engine 16 of a motor vehicle. The engine 16 is shownconnected to an idle speed control 18 which controls the idle speed ofthe engine 16. The generator 10 typically is driven at a higher speedthan the speed of the engine 16 by a belt and pulleys in a known manner.

The output terminals of the three phase stator winding 12 are connectedrespectively to AC input terminals of a three-phase full-wave bridgerectifier generally designated by reference numeral 20. The bridgerectifier 20 includes three positive semiconductor diodes 22 which havetheir cathodes connected to a direct voltage output terminal 24. Thebridge rectifier 20 also has three negative semiconductor diodes 26, theanodes of which are connected to a grounded direct current outputterminal 30 of the bridge rectifier 20.

The junction 32 that is connected between a pair of positive andnegative diodes is connected to the voltage regulation unit 4 at P1. Thevoltage that is developed at junction 32 is a pulsating voltage, and thefrequency of the voltage pulses developed at this junction 32 is afunction of generator and engine speed. When the generator is notrotating, it does not generate an output voltage and the voltage atjunction 32 is zero.

The signal at junction 32 therefore represents generator and enginespeed and also indicates whether or not the generator is rotating butonly if there is residual magnetism in the generator or if the voltageregulator 4 has been otherwise activated so that current flows throughthe field winding 14.

Connected to the charging system 2 is a storage battery 36. The negativeside of the storage battery 36 is grounded, and the positive side of thebattery 36 is connected to junction 38. The battery 36 will be assumedto be a 12 volt storage battery in the description of this invention,though it is understood that the invention is not limited in thisregard. The battery 36 is charged by a circuit that includes theconductor 40 that connects the direct voltage output terminal 24 of thebridge rectifier 20 to the junction 38. The direct voltage outputterminal 24 provides a positive voltage output with rippling as a resultof the multi-phase AC output currents generated by the generator 10. Thebattery 36 and generator 10 feed various electrical loads on the motorvehicle, which have not been illustrated but which are electricallyconnected between junction 38 and ground.

The voltage regulation unit 4 controls the current through field winding14 to regulate the voltage appearing between junction 38 and ground to adesired regulated value. In describing this invention it will be assumedthat the system is a 12 volt system and that the desired regulatedvoltage that is to be maintained between junction 38 and ground is about14 volts. This desired regulated voltage typically will vary withtemperature. Though the foregoing exemplary voltages (i.e., 12 and 14volts) are used in most of the preferred implementations, it isunderstood that the invention may be practiced using different voltages.

The current through field winding 14 is controlled by a semiconductorswitching device which takes the form of a metal oxide semiconductorfield effect transistor 42. This transistor is an N-channel enhancementmode type of transistor. The transistor 42 has a gate G connected toconductor 44, a drain D connected to junction 46 and a source Sconnected to one side of field winding 14. The opposite side of fieldwinding 14 is connected to ground. The junction 46 is connected to thepositive direct voltage output terminal 24 of the bridge rectifier 20via conductor 48. A field discharge diode 49 is connected across fieldwinding 14.

When the transistor 42 is biased conductive, between its drain D andsource S, the field winding 14 will be energized via a circuit that canbe traced from the positive direct voltage output terminal 24, throughconductor 48 to junction 46, through the drain D and source S electrodesof transistor 42 and then through the field winding 14 to ground. Thetransistor 42 is switched on and off, in a manner known in the art, inorder to maintain the voltage at junction 38 at the desired regulatedvalue which has been assumed to be about 14 volts. The field winding 14also can be energized from battery 36 via conductors 40 and 48 andtransistor 42.

Biasing of the transistor 42 is controlled by the voltage regulationunit 4, the voltage regulation unit 4 can be programmed or otherwisesuitably configured to selectively control biasing of the transistor 42in a manner dependent upon the rotational speed of the engine 16 and/orgenerator 10 (i.e. the rotational speed of the field winding 14). Anexample of this type of control is disclosed in the Bowman et al.patent. Such voltage regulation units 4 can be used, as indicated above,to minimize the increased torque load that is applied to the engine 16by the generator 10 when a large electrical load is applied to thegenerator 10 at the time that the engine 16 and generator 10 areoperating at a low speed, such as engine idle speed.

In addition, and in accordance with an exemplary embodiment, the voltageregulation unit is programmed to also control the biasing of transistor42 in response to the comparator output of a pair of signals (P1 andP2).

The voltage regulation unit 4 thus is adapted to receive a pair ofspeed-indicative signals P1 and P2. Signal P1 is indicative of thevoltage at junction 32 and signal P2 is indicative of speed signalgenerated by apparatus 6. Signals P1 and P2 are inputted into voltageregulation unit 4. The voltage regulation unit 4 includes a comparator49 or equivalent for receiving and comparing signals P1 and P2 (FIG. 4).Comparator receives signals P1 and P2 and determines whether there isany differential between the two. If the generator is operating properlysignals P1 and P2 should cause comparator 49 to provide a zero output.See also FIG. 3.

If however, signals P1 and P2 are unequal an error or fault signal willbe generated on line 70 causing an indicator light 72 to the activated.In exemplary embodiment, indicator light 72 is positioned in a viewablelocation within the vehicle. Preferably, such viewable location is onthe vehicle dashboard.

One of the causes for signals P1 and P2 to be unequal is the failure toone of the diodes in the rectifier bridge. With a single means fordetermining the rotational speed of the alternator it is difficult todetermine whether one of the diodes is open, as the signal will miss oneof the filtering networks and change the frequency.

Thus, and with a smart regulator as contemplated in accordance with anexemplary embodiment of the present invention, the voltage regulationunit will be able to determine whether a diode is open and instruct thesystem to take the necessary steps in order to prevent further damage.For example, transistor 42 may be biased to reduce the load on thealternator thus reducing heat buildup on the other properly operatingdiodes. In addition, an indicator light is activated instructing avehicle operator to bring the vehicle in for service. Alternatively, thesystem may be shut down.

In addition, and in accordance with an exemplary embodiment of thepresent invention voltage regulation unit 4 is configured to biastransistor 42 in order to limit any damage capable of being caused by adefective diode.

A typical voltage regulation unit 4 responsive to engine and/orgenerator speed has a single control input P, often referred to as the“P input” or “Phase input.” One application of providing the controlinput P is to electrically connect the voltage regulation unit to thejunction 32 of the bridge rectifier 20.

However, and in accordance with an exemplary embodiment of the presentinvention voltage regulation unit not only receives an input P1 fromconnection 7 it also receives an input P2 from signal apparatus 6. Thespeed signal apparatus 6 is adapted to provide a speed-indicative signalSIS indicative of engine rotational speed and/or indicative of generatorrotational speed. The speed signal apparatus 6 comprises an input port50, speed signal circuitry 51, and an output port 52. The input port 50can be electrically connected to the positive voltage output from therectifier 20 at terminal 24. The speed signal circuitry 51 is connectedto the input port 50 and is adapted to convert rippling in the positivevoltage output at terminal 24 into the speed-indicative signal SIS. Theoutput port 52 is connected to the speed signal circuitry 51 and isadapted to apply the speed-indicative signal SIS to components outsideof the circuitry 51.

Preferably, as shown in FIG. 1, the output port 52 is connected to thevoltage regulation unit 4 so that the speed-indicative signal SIS isapplied to the control input P2 of the voltage regulation unit 4. Thespeed signal circuitry 51 preferably is adapted to apply thespeed-indicative signal SIS with a frequency of about one sixth afrequency of the rippling. The speed signal circuitry 51 also can beadapted to apply the speed-indicative signal SIS as a pulse train with afrequency of about one sixth a frequency of the rippling.

Preferably, the speed signal circuitry 51 includes a band pass filterand amplifier combination 53 that passes a range of frequencies in whicha frequency of the rippling substantially remains when the associatedengine 16 operates at rotational speeds of interest (e.g., low speedsand/or idle speed) and that also amplifies an AC component of therippling. An exemplary range of frequencies associated with idle speed(and/or low rotational speeds close to idle), is between about 50 and330 Hertz for a typical pulley rotation ratio of about 2.8-to-1. Thistypical pulley rotation ratio provides about 2.8 rotations of thegenerator's pulley for every rotation of the engine's crankshaft pulley.It is understood, however, that the range of frequencies passed by theband pass filter and amplifier combination 53 can be suitably adjustedfor different pulley rotation ratios, and that the present inventionunderstandably is not limited to the exemplary range of frequencies, noris it limited to the exemplary pulley rotation ratio.

Since the typical speed-responsive voltage regulation unit 4 uses therotational speed primarily to determine whether or not the engine isoperating at low speeds, such as idle speed, such low speeds typicallywill represent speeds of interest to the voltage regulation unit 4. Therange of frequencies passed by the band pass filter and amplifiercombination 53 therefore preferably includes typical frequenciesexhibited by the rippling when the engine 16 is idling or otherwiseoperating at a rotational speed to be treated substantially the same asidling by the voltage regulation unit 4. Since it may be desirable toprovide the voltage regulation unit 4 with the speed-indicative signaleven when the generator 10 is rotating faster than such low speeds(e.g., so that the voltage regulation unit 4 can verify that therotational speed, in fact, is higher than the speed of interest, or forother speed-responsive operations of the voltage regulation unit 4), theband pass filter and amplifier combination 53 can be adapted to passfrequency ranges other than those associated with idle speed or lowspeed operation of the engine 16.

Another exemplary range of frequencies that can be passed is from about80 Hertz to about 1.5 kilo Hertz. This range corresponds to generatorrotational speeds of about 800 generator r.p.m. to about 15,000generator r.p.m. With this exemplary range, the voltage regulation unit4 is able to verify, based on the speed-indicative signal, whether therotational speed of the generator 10 is higher than what is deemed bythe voltage regulation unit 4 to be low speed or idle operation. Thevoltage regulation unit 4 thus is able to confirm that the generator 10is rotating at rotational speeds higher than a threshold speed of, forexample, 3,000 r.p.m.

In typical applications of the voltage regulation unit 4, it mattersonly that the voltage regulation unit 4 verify that the rotational speedis higher than the threshold speed, and it does not matter how muchhigher. In other applications, however, it may be desirable to providethe voltage regulation unit 4 with signals indicative of speed at higherranges. The present invention therefore is not limited to the exemplaryband pass ranges described above, but rather can be practiced usingother ranges.

Preferably, the speed signal circuitry 51 includes a phase locked loop54. The phase locked loop 54 serves to minimize effects of noise on thespeed-indicative signal SIS, by locking onto the phase of the signal ofinterest (i.e., the ripple). The phase locked loop 54 can be implementedusing known combinations of circuit elements.

Because it is often desirable to apply the speed-indicative signal SISwith a frequency of about one sixth a frequency of the rippling, or as apulse train with a frequency of about one sixth the frequency of therippling, the circuitry 51 preferably includes a frequency divider 56(e.g., a divide-by-six counter).

With reference to FIG. 2, a preferred implementation of the circuitry 51of the speed signal apparatus 6 will be described. The following chartdescribes the components of the preferred circuitry 51 by referencenumber. The exemplary chip numbers correspond to National Semiconductorchip numbers that are known in the art. Inside the boxes that representthe integrated chips in FIG. 2 are the pin numbers, as assigned byNational Semiconductor.

REFERENCE NUMBER DESCRIPTION OF COMPONENT C1 1 micro farad capacitor C20.001 micro farad capacitor C3 0.01 micro farad capacitor C4 0.47 microfarad capacitor C5 0.001 micro farad capacitor C6 0.001 micro faradcapacitor R1 1 kilo ohm resistor R2 1 kilo ohm resistor R3 1 kilo ohmresistor R4 100 kilo ohm resistor R5 33 kilo ohm resistor R6 33 kilo ohmresistor R7 33 kilo ohm resistor PLL phase locked loop integrated chip(e.g., a 4046 chip) CO divide-by-six counter (e.g., a 4018 integratedchip) A1 Operational amplifier (op-amp)

The exemplary speed signal circuitry 51 operates in response to therippling on the positive voltage output from the rectifier 20 atterminal 24. In particular, the operational amplifier A1 amplifies an ACcomponent of the rippling, the band pass filter part of the combination53 passes the range of frequencies in which a frequency of the ripplingsubstantially remains during operation of the engine at rotationalspeeds of interest, and the frequency divider 56 (via counter CO)divides frequencies passed by the band pass filter part of thecombination 53 by a factor of about six to provide a frequency dividedsignal. The phase locked loop 54 is connected to the frequency divider56 and minimizes effects of electrical noise on the frequency dividedsignal. The phase locked loop 56 is arranged so that the frequencydivided signal is applied as the speed-indicative signal SIS.

Since the voltage regulation unit 4 consumes some energy, it typicallyis turned-off when the engine 16 is turned off. This prevents thebattery 36 from being drained by the voltage regulation unit 4,especially if the engine 16 remains off for a long period of time. Aslong as the engine 16 remains off, the voltage regulation unit 4 remainsoff. When the engine 16 is to be restarted, there is consequently a needto activate the voltage regulation unit 4.

Prior art arrangements use a connection from one or more of the statorwindings 12 to activate the voltage regulation unit 4 using residualmagnetism in the stator windings 12 or use a connection from theignition switch of the vehicle to activate the voltage regulation unit4. Those arrangements, however, suffer from certain disadvantages. Theresidual magnetism-based arrangements, for example, may not activate thevoltage regulation unit 4 if the residual magnetism has dissipated overtime (e.g., through diode leakage in the bridge rectifier 20), or if thegenerator 10 has been disassembled and then reassembled without“flashing” the voltage regulation unit 4. The arrangements having aconnection from the ignition switch require that extraneous connectionto be made, thereby requiring additional wiring to the regulator and/orgenerator that otherwise might not be required.

Those disadvantages can be avoided by providing an motion-basedactivation apparatus (not shown) that activates the voltage regulationunit 4 automatically when it detects vibration, motion, and/oracceleration indicative of rotation of the generator and/or engine. Anexemplary activation apparatus 6 is disclosed in commonly owned andassigned U.S. patent application entitled Apparatus and Method forMotion-Based Activation of a Voltage Regulator, 6,225,790, the contentsof which are incorporated herein by reference thereto, the apparatusrequires no external electrical connections that are not already presentat the voltage regulation unit 4. It also does not require externalelectrical connections that are not already present at the generator 10.The exemplary activation apparatus therefore can be integrated into thevoltage regulation unit 4 and/or generator 10. An integrated unit may bepreferred since it makes protection of the electrical connection betweenthe voltage regulation unit 4 and the activation apparatus moreeconomical and minimizes the likelihood of failure of such connectionsand any repair or warranty costs associated therewith. The activationapparatus alternatively can be implemented as a separate unit from thevoltage regulation unit 4 and/or generator 10, if such a design isdeemed acceptable or more desirable.

The exemplary speed signal apparatus 6 advantageously requires noexternal electrical connections that are not already present at thevoltage regulation unit 4. It also does not require external electricalconnections that are not already present at the generator 10. Theexemplary speed signal apparatus 6 therefore can be integrated into thevoltage regulation unit 4 and/or generator 10. An integrated unit may bepreferred since it makes protection of the electrical connection betweenthe voltage regulation unit 4 and the speed signal apparatus 6 moreeconomical and minimizes the likelihood of failure of such connectionsand any repair or warranty costs associated therewith. The speed signalapparatus 6 alternatively can be implemented as a separate unit from thevoltage regulation unit 4 and/or generator 10, if such a design isdeemed acceptable or more desirable.

As the foregoing description demonstrates, the present invention alsoincludes a method for providing a speed-indicative signal SIS indicativeof engine rotational speed or indicative of generator rotational speed.The method comprises the steps of detecting rippling in a positivevoltage output from a rectifier 20 of a generator 10, and converting therippling in the positive voltage output into a speed-indicative signalSIS indicative of engine rotational speed or indicative of generatorrotational speed.

Preferably, the speed-indicative signal SIS is applied to a controlinput of a voltage regulation unit 4. In the case of conventionalspeed-responsive voltage regulators, the speed-indicative signal SIS canbe applied to the “P2” or “Phase2” input of the voltage regulation unit4. Preferably, the step of converting the rippling is performed so thatthe speed-indicative signal SIS has a frequency of about one sixth afrequency of the rippling, and preferably is applied as a pulse train.The method also can include the step of filtering the rippling to pass arange of frequencies in which a frequency of the rippling substantiallyremains when the associated engine 16 operates at rotational speeds ofinterest. In doing so, the DC component of the positive voltage outputis filtered out. An exemplary range of band pass frequencies is betweenabout 50 and 3300 Hertz. Another exemplary range is between about 80Hertz and about 1.5 kilo Hertz.

The range of frequencies preferably includes typical frequenciesexhibited by the rippling when the engine 16 is idling or otherwiseoperating at a rotational speed to be treated substantially the same asidling by a voltage regulation unit 4. The range of frequencies also caninclude higher frequencies when the rotational speeds associatedtherewith are of interest (e.g., when they are of interest to a voltageregulation unit 4).

The method also can include the step of minimizing effects of noise onthe speed-indicative signal SIS, using a phase locked loop 54.Preferably, the method further includes the step of amplifying an ACcomponent of the rippling.

As shown in FIG. 3, the input port 50 of the speed signal apparatus 6preferably receives a substantially DC signal V₂₄ at about 14 volts withrippling as a result of the current outputs from the rectifier 20. Theillustrated rippling is typical when the load on the terminal 24 isgreater than 10 amperes. When this rippled signal is applied to theinput port 50, the amplifier and band pass filter combination 53 passand amplify the AC component of the rippling, and apply the result tothe phase locked loop 54. The output of the phase locked loop is a pulsetrain PT having substantially the same frequency as the rippling. Thispulse train PT is applied to the divide-by-six counter CO to provide afrequency divided version of the pulse train PT. This frequency dividedversion of the pulse train PT then is applied to the output port 52 asthe speed-indicative signal SIS. For purposes of comparison, FIG. 3 alsoshows the voltage V₃₂ that appears at junction 32.

It is clear from FIG. 3 that the speed-indicative signal SIS can beinputted into a comparator for comparison to V₃₂.

Since, as indicated above, the speed signal apparatus 6 can beintegrated into a voltage regulator 60, the present invention alsoprovides a voltage regulator 60 that is responsive to the rotationalspeed of the engine 16 and/or generator 10. The voltage regulator 60includes the voltage regulation unit 4 shown in FIG. 1 and the exemplaryspeed signal apparatus 6. The voltage regulation unit 4 is adapted tocontrol a field current of the generator 10 and has a pair of controlinputs (e.g., a “P1 input, P2 input” or “phase inputs”) adapted toreceive the speed-indicative signal SIS and the input signal from node32.

The speed signal apparatus 6, as indicated above, is adapted to providethe speed-indicative signal based on the rippling in the positivevoltage output of the rectifier 20.

Since the voltage regulator 60 defined by voltage regulation unit 4 andspeed signal apparatus 6 can be incorporated conveniently into anexisting generator 10, without requiring any electrical connection thatis not already required by the generator 10 itself, the voltageregulator 60 advantageously can have its internal components andinternal electrical connections protected from exposure or damage. This,in turn, provides a more reliable overall charging system/voltageregulating arrangement.

A reliable and versatile charging system 2 thus can be provided byinstalling the speed signal apparatus 6 in association with the voltageregulation unit 4 or by incorporating it into an integrated voltageregulator 60 of the charging system. The charging system 2 includes thegenerator 10, the rectifier 20, the speed signal apparatus 6, and thevoltage regulation unit 4 or regulator 60.

Based on the speed-indicative signal SIS, the voltage regulator 60 (orvoltage regulation unit 4) of the charging system 2 is able to controlelectrical current through the field winding 14 of the generator 10 in amanner at least partially dependent upon engine rotational speed orgenerator rotational speed. In addition, the voltage regulator 60 (orvoltage regulation unit 4) is also capable of monitoring failure ofcomponent parts of the generator.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. An apparatus for comparing a pair ofspeed-indicative signals indicative of engine rotational speed orindicative of generator rotational speed, comprising: an input port forelectrical connection to a positive voltage output from a rectifier of agenerator; speed signal circuitry connected to the input port andconfigured to convert rippling in said positive voltage output into aspeed-indicative signal indicative of engine rotational speed orindicative of generator rotational speed; an output port connected tosaid circuitry for applying said speed-indicative signal to acomparator; and a means for providing a voltage signal indicative of avoltage across a rectifier bridge of an alternator, said voltage signalbeing received by said comparator, wherein said comparator is configuredto indicated whether a diode of said rectifier bridge is open orinoperative by comparing said speed-indicative signal and said voltagesignal.
 2. The apparatus as in claim 1, wherein said comparator providesa comparator output indicating any differential between said voltagesignal and said speed-indicative signal.
 3. The apparatus as in claim 2,wherein said comparator output is inputted into a voltage regulationunit, said voltage regulation unit modifying the output of saidalternator in response to the value of said comparator output.
 4. Theapparatus as in claim 3, wherein an indicator light is activated whensaid comparator output indicates a differential between said voltagesignal and said speed-indicative signal.
 5. The apparatus as in claim 2,wherein said speed signal circuitry is configured to apply saidspeed-indicative signal with a frequency of about one sixth a frequencyof the rippling.
 6. The apparatus as in claim 2, wherein said speedsignal circuitry is configured to apply said speed-indicative signal asa pulse train with a frequency of about one sixth a frequency of therippling.
 7. The apparatus as in claim 2, wherein said speed signalcircuitry includes a band pass filter that passes a range of frequenciesin which a frequency of said rippling substantially remains when theengine operates at rotational speeds of interest.
 8. The apparatus as inclaim 7, wherein said range of frequencies is between about 80 and about1,500 Hertz.
 9. The apparatus as in claim 7, wherein said range offrequencies includes typical frequencies exhibited by the rippling whenthe engine is idling or otherwise operating at a rotational speed to betreated substantially the same as idling by a voltage regulator.
 10. Theapparatus as in claim 2, wherein said speed signal circuitry includes aphase locked loop.
 11. The apparatus as in claim 2, wherein said speedsignal circuitry includes an amplifier to amplify an AC component ofsaid rippling.
 12. The apparatus as in claim 2, wherein said speedsignal circuitry includes: an amplifier to amplify an AC component ofsaid rippling; a band pass filter to pass a range of frequencies inwhich a frequency of said rippling substantially remains duringoperation of the engine at rotational speeds of interest; a frequencydivider to divide frequencies passed by said band pass filter by afactor of about six to provide a frequency divided signal; and a phaselocked loop connected to said frequency divider and to control effectsof electrical noise on said frequency divided signal, said phase lockedloop being arranged so that said frequency divided signal is applied assaid speed-indicative signal.
 13. A method for providing a signalindicative of an alternator operation, comprising: determining a firstspeed-indicative signal indicative of engine rotational speed orindicative of generator rotational speed by detecting rippling in apositive voltage output from a rectifier of a generator, converting saidrippling in said positive voltage output into a speed-indicative signalindicative of engine rotational speed or indicative of generatorrotational speed; comparing said first speed-indicative signal to avoltage signal across said rectifier; and providing a comparative outputsignal corresponding to the difference between said firstspeed-indicative signal and said voltage signal, wherein said comparatoroutput signal indicates whether a diode of said rectifier bridge is openor inoperative.
 14. The method as in claim 13, further comprising thestep of applying said speed-indicative signal and said voltage signal tocontrol inputs of a voltage regulator.
 15. The method as in claim 14,wherein said voltage regulator modifies the operation of said alternatorin response to said comparator output signal.
 16. The method as in claim14, wherein said voltage regulator includes a means for providing saidcomparator output.
 17. The method as in claim 14, wherein saidcomparator output signal is used to provide a signal to an indicatorlight, said indicator light indicating that the operation of saidalternator is outside a preferred operational range.
 18. The method asin claim 13, wherein said step of converting said rippling is performedso that the speed-indicative signal has a frequency of about one sixth afrequency of the rippling.
 19. The method as in claim 13, wherein saidstep of converting said rippling is performed so that saidspeed-indicative signal is a pulse train with a frequency of about onesixth a frequency of the rippling.
 20. The method as in claim 13,further comprising the step of filtering said rippling to pass a rangeof frequencies in which a frequency of said rippling substantiallyremains when an associated engine operates at rotational speeds ofinterest.
 21. The method as in claim 20, wherein said range offrequencies is between about 80 and about 1,500 Hertz.
 22. The method asin claim 20, wherein said range of frequencies includes typicalfrequencies exhibited by the rippling when the engine is idling orotherwise operating at a rotational speed to be treated substantiallythe same as idling by a voltage regulator.
 23. The method as in claim13, further comprising the step of minimizing effects of noise on saidspeed-indicative signal, using a phase locked loop.
 24. The method as inclaim 13, wherein said step of converting the rippling includes the stepof amplifying an AC component of said rippling.
 25. The method as inclaim 13, wherein said step of converting the ripping includes the stepsof: amplifying an AC component of said rippling; filtering said ripplingto pass a range of frequencies in which a frequency of said ripplingsubstantially remains during operation of an associated engine atrotational speeds of interest; frequency dividing frequencies passed bysaid filtering by a factor of about six to provide a frequency dividedsignal; and controlling effects of electrical noise on said frequencydivided signal using a phase locked loop.
 26. A generator for use withan engine and an electric storage medium, the generator comprising: avoltage regulation unit for controlling a current through a fieldwinding of the generator; a speed signal apparatus for generating aspeed signal of the generator or the engine; a rectifier bridge having aplurality of positive and negative diode; and a comparator for receivingand comparing said speed signal and a voltage generated between saidplurality of positive and negative diodes, wherein said comparatorprovides a signal indicating whether one of said plurality of positiveand negative diodes is open or inoperative.
 27. The generator as inclaim 26, wherein said speed signal apparatus comprises: an input portfor electrical connection to a positive voltage output from saidrectifier; speed signal circuitry connected to the input port andconfigured to convert rippling in said positive voltage output into saidspeed signal; and an output port connected to said speed signalcircuitry and said comparator.
 28. The generator as in claim 27, whereinsaid speed signal circuitry performs the method of: amplifying and ACcomponent of said rippling; filtering said rippling to pass a range offrequencies in which a frequency of said rippling substantially remainsduring operation of rotational speed of interest of the engine;frequency dividing frequencies passed by a band pass filter by a factorof about six to provide a frequency divided signal; and controllingeffects of electrical noise on said frequency divided signal using aphase locked loop.